U.S. Pat. No. 2,447,947 to Larson et al issued Aug. 12, 1948 describes a variable pipe coupling for connecting the ends of two pipes in a variety of angles from straight to virtually 90.degree.. It is a stated object of that invention to provide a coupling that does not in any way restrict the flow of fluid passing therein. The design of the Larson coupling is such that, particularly in severely angled configurations, the interior surface defines a bulbous chamber.
U.S. Pat. No. 5,064,226 to Klas issued Nov. 12, 1991 describes a nonmetallic conduit fitting with transverse biasing adjustments which comprises a pair of coaxial, rotatably coupled, straight tubular members having a series of angularly disposed internal latching tabs which permit assembly in a variety of angular configurations.
While the basic design of the Larson coupling is quite satisfactory for fluids, it is relatively unsatisfactory for use as a coupling for electrical conduit. The bulbous chamber referred to hereinabove results in a configuration which, while adequate to provide relatively uninterrupted flow of a fluid, does not provide a smooth transition between coupling segments. Thus, an electrical or communications cable cannot be readily fed therethrough without some twisting, maneuvering or pushing that might damage the wire or cable being so inserted.
The coupling of Klas, while similarly quite useful, is complicated, because of the tabular arrangement, relatively more difficult to assemble and requires the use of an O-ring to provide water resistance.